Erosion is no laughing matter, people. As I read on the front page of this Sunday’s Boston Globe, one of my favorite beaches is closed for the next two weeks as the stairs (which are insane, and totally unsafe when crowded by tourists and their umbrellas and inflatable alligators) are rebuilt. Marconi and the rest of the Cape’s National Seashore, which includes Nauset and Coast Guard, have been hit by…